Recently, relating to the currency of global carbon dioxide emission limits accompanying increased concerns with environment problem, requirement for fuel consumption reduction of automobiles is increasing. In order to satisfy such requirement, with respect to tire performances, reduction of rolling resistance is desired as well. Simultaneously, requirement for safety has increased as well, and achievement of both rolling resistance and safety (in particular, gripping performance on wet road surface) of tire is strongly desired.
In such background, there is a tendency of increase of compounding silica to rubber composition. A rubber composition with a silica compounded has small hysteresis loss (i.e., excellent low loss property), and it is possible to reduce rolling resistance of a tire by applying a rubber composition with small hysteresis loss to the tire. Moreover, by applying a rubber composition with a silica compounded to a tread rubber of a tire, it is possible to improve the gripping performance on wet road surface of the tire. However, silica aggregates in the rubber composition, and thus there is a problem of processability (operability).
Regarding this, as a chemical for improving the dispersibility of silica in rubber composition and improving the processability, a glycerin fatty acid ester as described in WO 2014/098155 A1 (PTL1), etc. has been developed.